Many different types of mechanical devices are provided having pressurized fluid systems for operation thereof. The present invention, though being described particularly as it relates to double acting hydraulic motors such as is commonly used in paint pumps and the like, has a wide variety of applications in various and sundry fluid energized mechanisms wherein the methods of the present invention are applicable. The term "fluid" as utilized herein is intended to encompass a wide variety of liquid compositions including water, oil such as hydraulic oil and various other compositions including a liquid as a material constituent thereof. The term "liquid" as utilized herein is intended to mean any material or composition of materials capable of flowing, without regard to the particular viscosity thereof.
The use of hydraulic cylinders for a variety of mechanical applications is well known. In general, great care is taken in the design of the seals around the moving piston to prevent leakage of hydraulic oil out of the system. In spite of the best seal technology available, leakage is inevitable as the seals and piston wear during normal use of the apparatus. In most cases the initial leakage is small and is generally accepted. The hydraulic reservoir of the apparatus is refilled occasionally to replace the lost fluid.
In some applications any degree of leakage can have serious effect. One such application is a hydraulically operated paint pump which can be used to deliver paint to spray guns in industrial plants. Leakage of oil in this environment, even though slight, over extended periods of time can result in contamination of the paint supply. In some instances paint is stored in large containers and oil contamination can be very expensive because of the expensive paint that must be discarded as unusable. This invention pertains to a method for automatically and inexpensively collecting oil which leaks from the cylinder and directing the leaked oil back into the hydraulic system, thus preventing it from causing contamination to materials or apparatus externally of the fluid energized motor or device.
Many different types of mechanical devices, such as the hydraulic motors for paint pumps, incorporate a housing structure having internal movable components and form or otherwise incorporate a pressurized fluid system for operation thereof. In most cases, the mechanical device, to provide a work output, will have an output shaft that rotates, reciprocates or includes a combination of rotation and reciprocation in its movement. The housing structure of the apparatus in such cases defines a passage through which the output shaft extends and a seal, such as a resilient O-ring or any other commercially available sealing device is utilized to establish a seal between the output shaft and the housing. Obviously these sealing devices are always designed to prevent leakage of liquid materials such as lubricating oils, hydraulic oil, etc. from the mechanical device. Through normal wear, unusual seal erosion or other character of seal deterioration leakage will develop in time. In some cases, a small amount of leakage is tolerated until the apparatus can be shut down for repair. In many cases, especially in the cases of fluid motors for paint pumps, even a small amount of leakage can cause contamination of a large volume of paint, thereby requiring that the paint be discarded. In mechanical devices where even minimal seal leakage is undesirable the present invention has application. It is therefore desirable to provide an anti-leakage system for mechanical apparatus having a fluid energized system for operation thereof or a fluid system providing other necessary features such as lubrication, cooling, etc.